(1) Field of the Invention
The present invention relates to an electric drive system. More particularly the system comprises a control and indicator unit that directs the operation of at least one submersible brushless direct current motor with each motor having a 6-step, variable-bus motor controller.
(2) Description of the Prior Art
Before the development of thin-line arrays (TLA), towed arrays were large in diameter, (e.g., 3 in.), and shorter than the length of a submarine.
Large-diameter arrays currently in use in the Fleet are towed on a long cable behind the submarine. The cable is stowed on a reel inside the submarine pressure hull, while the large-diameter array is stowed in the free-flooding area outside the submarine pressure hull.
Advances in Soviet ship silencing have made their submarines quieter and less detectable by our large-diameter arrays. The large-diameter towed array had to be made longer to improve its performance. The longer array had to be made thinner, in order to reduce the drag produced by pulling it through the water and to make it stowable on the submarine when
In 1978, the Navy began development of the TB-23/BQ TLA. Because the TB-23/BQ TLA was significantly longer than a submarine, it was stored with the tow cable on a reel external to the submarine pressure hull. This external reel requirement led to the development of two handling systems. The choice of which of the two handling systems was used depended on the class of the submarine. Both of these handling systems were powered by hydraulic motors. These hydraulic motors were located external to the pressure hull in the sea water environment. Use of hydraulic motors external to the pressure hull represented a precedent in that although hydraulics had long been used to power external machinery, the hydraulic components had always been located inside the pressure hull and connected to the external machinery by a through hull drive shaft. The hydraulic motors were used, however, because of the lack of an available electric alternative having the combined power, control, reliability, and structureborne noise characteristics required for driving a cable stowage reel or a cable drive unit under water.